Ba3SnGa10- xInxO20 (0 ≤ x ≤ 2): site-selective doping, band structure engineering and photocatalytic overall water splitting

Abstract

Developing new photocatalysts and deciphering the structure-property relationship are always the central topics in photocatalysis. In this study, a new photocatalyst Ba₃SnGa₁₀O₂₀ containing two d¹⁰ metal cations was prepared by a high temperature solid state reaction, and its crystal structure was investigated by Rietveld refinements of monochromatic X-ray powder diffraction data for the first time. There are 2 Ba, 4 metal cations and 6 O independent atoms in a unit cell. Sn⁴⁺ and Ga³⁺ co-occupy the octahedral cavities named M1 and M2 sites, and the other two metal sites are fully occupied by Ga³⁺. Rational In³⁺-to-Ga³⁺ substitution was performed to reduce the potential of the conduction band minimum and enhance the light absorption ability, which was indeed confirmed using UV-vis diffuse reflectance spectra and Mott-Schottky plots for Ba₃SnGa_10-xIn_xO₂₀ (0 ≤ x ≤ 2). Interestingly, In³⁺ exhibits site selective doping at M1 and M2 sites exclusively. With the light absorption ability enhanced, the photocatalytic overall water splitting activity was also improved, i.e. the photocatalytic H₂ generation rate was 1.7(1) μmol h^-1 for Ba₃SnGa₁₀O₂₀, and the optimal catalyst Ba₃SnGa_8.5In_1.5O₂₀ loaded with 1.0 wt% Pd exhibited the H₂ generation rate of 27.5(4) μmol h^-1 and the apparent quantum yield at 254 nm was estimated to be 2.28% in pure water.